public class MyLinkedList {

    static class ListNode{
        public int val;
        public ListNode prev;
        public ListNode next;

        public ListNode(int val) {
            this.val = val;
        }
    }

    public ListNode head;
    public ListNode last;

        //头插法
        public void addFirst(int data){
            ListNode node = new ListNode(data);
            if(head == null){
                head = node;
                last = node;
            }else{
                node.next = head;
                head.prev = node;
                head = node;
            }
        }

        //尾插法
        public void addLast(int data){
            ListNode node = new ListNode(data);
            if(head == null){
                head = null;
                last = null;
            }else{
                last.next = node;
                node.prev = last;
                last = node;
            }
        }

        //任意位置插入,第一个数据节点为0号下标
        public void addIndex(int index,int data){
            if(index < 0 || index > size()){
                System.out.println("下标超出范围");
                return ;
            }
            if(index == 0){
                addFirst(data);
                return ;
            }
            if(index == size()){
                addLast(data);
                return ;
            }
            ListNode node = new ListNode(data);
            ListNode cur = searchIndex(index);
            cur.prev.next = node;
            node.next = cur;
            cur.prev = node;
        }

        public ListNode searchIndex(int index){
            ListNode cur = head;
            while(index != 0){
                cur = cur.next;
                index--;
            }
            return cur;
        }

        //查找是否包含关键字key是否在单链表当中
        public boolean contains(int key){
            if(head == null){
                return false;
            }
            ListNode cur = head;
            while(cur != null){
                if(cur.val == key){
                    return true;
                }
                cur = cur.next;
            }
            return false;
        }

        //删除第一次出现关键字为key的节点
        public void remove(int key){
            if(head == null){
                System.out.println("链表为空");
                return ;
            }
            ListNode cur = head;
            while(cur != null){
                if(cur.val == key){
                    if(cur == head){
                        head = head.next;
                        if(head != null){
                            head.prev = null;
                        }
                    }else{
                        cur.prev.next = cur.next;
                        if(cur.next == null) {
//                            cur.prev.next = cur.next;
                            last = cur.prev;

                        }else {
//                            cur.prev.next = cur.next;
                            cur.next.prev = cur.prev;

                        }
                    }
                    return ;
                }else{
                    cur = cur.next;
                }
            }
            System.out.println("没有该数");
        }

        //删除所有值为key的节点
        public void removeAllKey(int key) {
            if (head == null) {
                System.out.println("链表为空");
                return;
            }
            int count = size();
            ListNode cur = head;
            while (cur != null) {
                if (cur.val == key) {
                    if (cur == head) {
                        head = head.next;
                        if (head != null) {
                            head.prev = null;
                        } else {
                            last = null;
                        }
                    } else {
                        cur.prev.next = cur.next;
                        if (cur.next == null) {
//                            cur.prev.next = cur.next;
                            last = cur.prev;

                        } else {
//                            cur.prev.next = cur.next;
                            cur.next.prev = cur.prev;

                        }
                    }
                }
                cur = cur.next;
            }
            if (count == size()) {
                System.out.println("没有该数");
            }
        }

        //得到单链表的长度
        public int size(){
            ListNode cur = head;
            int count = 0;
            while(cur != null){
                cur = cur.next;
                count++;
            }
            return count;
        }

        public void display(){
            ListNode cur = head;
            while(cur != null){
                System.out.print(cur.val + " ");
                cur = cur.next;
            }
            System.out.println();
        }

        public void clear(){
            ListNode cur = head;
            while(cur != null){
                ListNode curN = cur.next;
                cur.prev = null;
                cur.next = null;
                cur = curN;
            }
            head = null;
            last = null;
        }



}
